This invention relates to an operative device for a valve controlled by human hands, and more particularly relates to the device for a model in which an opening and a closing of the valve are arranged by rotating the valve body.
In prior art, valves have been well known such as butterfly valves, ball valves, cocks and so on, where a rotation of the valve is adapted to open or close a flow passage and is adapted to control various kinds of fluid flows. Among these rotating valves, a valve having a small diameter is often equipped witfh manual operation by means of an operative lever or the like which is built at the outer end of an extending stem.
Ball valves or cocks are so well restrained by the given pressure of a valve seat that an opening angle or degree is never influenced by changes of fluid pressure or changes of fluid speed. Therefore, for this kind of valve, it is not necessary to prepare an extra means of manual operative lever at the intermediate opening degree.
On the other hand, for butterfly valves, the valve body is not strained properly on account of their constructions, so that some unblanced torque may be imposed because of the changes of fluid pressures or the changes of fluid speed, and thus the opening degree is badly influenced. Accordingly, it is necessary to fix some extra means of manual operative lever thereagainst. For example, a plate with a notch is formed, while a projection is also formed on the top end of the lever to engage with the notch correctly. Or else, an extra screw is fastened to the lever, so that the lever may not move unexpectedly.
For rotating valves, the amount of rotation is usually set at a 90 degree angle, and a stopper is provided to prevent overrun of the opening position and also to control the minimum or maximum opening position.
The notch, screw and stopper are positioned at the outside surface of the operative device, and therefore these portions are easily deformed or broken with an outer shock or accidental blow. Sometimes, the engagement between the notch and the projection is disconnected to result into erroneous operation. Especially for the lever, it largely stands extending toward the outside, which invites the contact of workers in the factory, where the lever is wrongly operated to change the opening degree.